Generic unbalanced shafts are disclosed in DE 10 2007 009 800 A1 and DE 10 2007 027 990 A1. These achieve a significant reduction of mass of the unbalanced shaft by the fact that not only the shaft sections but also the bearing journals participate in the production of the shaft unbalance. For this purpose, the bearing journals possess the shape of a fractional cylinder having a cross-sectional surface that is substantially mirror symmetrical to the likewise rotating unbalance direction and whose planar center of gravity is eccentric to the axis of rotation in unbalance direction. The circular arc-shaped outer peripheral surface of the fractional cylinder is completed into a full cylinder through a bearing ring or a bearing ring piece joined thereto for obtaining a closed inner raceway, i.e. a raceway extending through 360° for the rolling elements of a rolling bearing that serves for a low-friction mounting of the unbalanced shaft in the internal combustion engine.
In contrast to hydrodynamic sliding bearings, it is possible in rolling bearing-mounted unbalanced shafts to omit the pressurized lubricant supply to the bearing journals and replace it with a pressure-less lubricant supply. According to EP 1 775 484 A2, this can be realized through the oil mist formed during operation, an adequate quantity of which reaches the rolling elements which project locally from the outer periphery of the variable-width bearing journal. In the case of the initially cited documents, however, there exists a danger of a wear-promoting deficient lubrication of the rolling contact between the rolling elements and the inner raceway because the inner raceway is a completely closed inner raceway without adequate lubricant access into the interior of the rolling bearing.